On Thu, 19 Oct 1995, Steve Rogers wrote:
> Hi. Can anyone explain why certain brain structures (e.g. substantia
> nigra) contain the black pigment, melanin? Thanks in advance.
>> ****************************************************
> Steve Rogers
> Dept. of Cell & Structural Biology and the
> Beckman Institute - Optical Visualization Facility
> Univ. of Illinois @ C-U
>srogers at delphi.beckman.uiuc.edu> ****************************************************
These are guesses based on something I read a long time ago, but forgot
where:
1) Before mammals had a thick skull, light entered the brain, and there
were pigmented sensory structures there that detected light and used that
light info to synchronize diurnal rythyms. The pineal has been called
the third eye for this reason in fish (I think).
2) Maybe melanin is a by-product of dopamine production or melatonin
production.
3) It could be structural (but I doubt it). Pigments are sometimes used
to give strength to body parts, I've seen pigment cells wrapped around
arterioles in lower vertebrates for this reason, and bird primary
feathers are almost always strengthened by the presence of melanin.
A very interesting question; please post here if you get an answer.
Sandra
----------------------
sandraw at U.Arizona.EDU
